• 대한기계학회논문집A
• /
• 제20권7호
• /
• pp.2148-2158
• /
• 1996

Uncoupled, quasi-static and linear thermoviscoelastic problems are analyzed in time domain by the finite element approximation which is developed using the principle of virtual work and viscoelasticity matrices instead of shear and bulk relaxation functions as in usual formulations. The material is assumed to be isotropic, homegeneous and thermorheologically simple, which means that the temperature-time equivalence postulate is effective. The stress-strain laws are expressed by relaxation-type hereditary integrals. In spatial and time discritizations, isoparametric quadratic quadrilateral finite elements and linear time variations are adopted. For explicit derivations, the viscoelastic material is assumed to behave standard linear solid in shear and elastically in dilatation. Two-dimensional examples are solved under general temperature distributions T = T(x, t), and compared with other opproximate solutions to show the versatility of the presented analysis.

• 무역학회지
• /
• 제46권2호
• /
• pp.107-119
• /
• 2021

Using a trade policy, government can shift profits from foreign firms to domestic firms. This paper will reexamine how asymmetric information can affect the equivalence of tariff and quota in a duopoly, where one domestic firm competes with one foreign firm. It can happen that the domestic firm has informational advantage against the government. Within this framework, the domestic firm has private information about own marginal cost as well as the foreign firm's. The domestic firm would exploit the advantage to draw a favorable policy from the government. When the government is misled, social welfare would decline. This paper will guide how the government can extract information from the domestic firm by offering a menu of tariff or quota. Previous studies showed that quota demands information more than tariff. With the principle of revealed information, the domestic firm chooses tariff (quota) if the marginal cost of foreign firm is low (high). The quota level will be high (low) if the marginal cost of domestic firm is high (low). To prevent misrepresentation, the domestic firm should be charged when quota is implemented. When the quota level is low, the domestic firm is charged additionally. This paper can contribute to the literature of trade policy and information.

• 한국연소학회지
• /
• 제16권3호
• /
• pp.12-20
• /
• 2011

Oxy-coal combustion for $CO_2$ capture in coal power plants entails a mode switching from air-firing to oxyfiring. In this study, procedure of the mode switching was investigated and discussed through experiments in pilot scale facilities: (1) a 0.3 $MW_{th}$ furnace with a vertical single burner and a FGR(Flue Gas Recirculation) system (2) a 1 $MW_{th}$ furnace with horizontal 4 burners and a FGR system. Principle of the mode switching was established and performed with control of FD fan, FGR fan, ID fan and oxygen flow rates. We have found that equivalence ratio in the oxy-firing mode should be increased more than that in the air-firing to achieve stable mode switching. Control of FD, ID and FGR fans should be performed carefully in the mode switching, in the sense of complete combustion and flame attachment. Moisture contents in the ash and the flue gas recycled to the primary oxidizer stream should be removed to prevent condensation, corrosion and duct clogging.

• 한국항행학회논문지
• /
• 제5권1호
• /
• pp.85-96
• /
• 2001

최근에 통합 설계 최적화 프로그램인 $ASTROS^*$와 Aeroservoelasticity(ASE) 모듈에 지능구조물의 해석 모듈을 통합하는 연구가 수행되었다. 통합된 소프트웨어를 이용해 플러터 억제 시스템을 설계하는 연구를 F-16모델을 이용해 수행하였으며 능동 제어 시스템을 위하여 신경망을 이용한 제어기가 설계되었다. 압전작동기에 의해 발생한 변형을 고려하기 위해 지능구조물 모듈은 $ASTROS^*$내의 열응력 해석 모듈을 개량하여 개발되었으며 ASE내에서 조종면을 이용한 입력과 압전작동기를 이용한 입력의 상호 호환성을 가능하게 하였다. 수치 예를 통해 개발된 제어시스템이 플러터속도를 증가시키는 데 효과적임을 보였다.

• 센서학회지
• /
• 제8권1호
• /
• pp.63-68
• /
• 1999

CCD 카메라에 얻어진 비디오 신호로부터 디지털화된 얼굴영상을 얻은 다음 신속하게 눈 패턴을 검출할 수 있는 알고리즘을 제안하였다. 얼굴영역 및 눈 패턴 검출을 위해 주축성분분석(Principle Component Analysis : PCA)과 통계적인 성질이 유사한 일괄처리 SVD(Singular Value Decomposition)알고리즘 및 패턴서치회로망을 이용하였고, 정확도를 향상하기 위해 HMM(Hidden Markov Model)을 이용하였다. 제안한 알고리즘으로 기존의 주축성분분석을 이용한 패턴 검출보다 계산량이 적고 정확도도 우수하며 초당 2 프레임 정도의 실시간 처리가 가능함을 알 수 있었다.

• 한국융합학회논문지
• /
• 제6권5호
• /
• pp.9-14
• /
• 2015

본 논문에서는 유전체 표면을 소형의 패치로 분해한 다음에 각 패치의 유도전류를 구하는 모먼트법(MoM)과 전체 유전체 표면의 입사전파와 반사 및 침투 전파의 합을 구하는 적분방정식을 융합하여 유전물질로 구성된 육면체의 유도전류 분석하였다. 평면파 전자파가 입사될 때 임의모형의 유전체에 유도되는 유도전류는 일반적으로 수치해석방법을 적용하여 계산하는 것이 정확하며 사용한 적분방정식은 5 명의 과학자가 공동으로 제안한 PMCHW 방정식을 사용하였다. MoM에 사용된 패치는 삼각형 패치를 사용하고 기초함수는 광대역 주파수에 사용할 수 있는 Loop-Patch 기초함수를 사용하였다. 제안된 계산방식은 넒은 주파수 범위에서 임의 모형의 유전체에 대해서 적용할 수 있으며 유전체 육면체의 유도전류를 분석하여 제시하였다.

• Steel and Composite Structures
• /
• 제18권4호
• /
• pp.853-871
• /
• 2015

Up to now, Japan has more than 200 corrugated steel web composite beam bridges which are under construction and have been constructed, and China has more than 30 corrugated steel web composite beam bridges. The bridge type includes the simply supported beam, continuous beam, continuous rigid frame and cable stayed bridge etc. The section form has developed to the single box and multi-cell box girder from the original single box and single chamber. From the stress performance and cost saving, the span range of 50~150 m is the most competitive. At present, the design mostly adopts the computational analytical method combining the spatial bar system model, plane beam grillage model and solid model. However, the spatial bar system model is short of the refinement analysis on the space effect, such as the shear lag effect, effective distribution width problem, and eccentric load factor problem etc. Due to the similarity of the plane beam grillage method in the equivalence principle, it cannot accurately reflect the shearing stress distribution and local stress of the top and bottom plates of the box type composite beam. The solid model is very difficult to combine with the overall calculation. Moreover, the spatial grid model can achieve the refinement analysis, with the integrity of the analysis and the comprehensiveness of the stress checking calculation, and can make up the deficiency of the analytical method currently. Through the example verification of the solid model and spatial grid model, it can be seen that the calculation results for the stress and the displacement of two models are almost consistent, indicating the applicability and precision of the spatial grid model.

• Coupled systems mechanics
• /
• 제12권3호
• /
• pp.199-220
• /
• 2023

This article presents a new analytical model to study the effect of porosity on the shear correction factors (SCFs) of functionally graded porous beams (FGPB). For this analysis, uneven and logarithmic-uneven porosity functions are adopted to be distributed through the thickness of the FGP beams. Critical to the application of this theory is a determination of the correction factor, which appears as a coefficient in the expression for the transverse shear stress resultant; to compensate for the assumption that the shear strain is uniform through the depth of the cross-section. Using the energy equivalence principle, a general expression is derived from the static SCFs in FGPB. The resulting expression is consistent with the variationally derived results of Reissner's analysis when the latter are reduced from the two-dimensional case (plate) to the one-dimensional one (beam). A convenient algebraic form of the solution is presented and new study cases are given to illustrate the applicability of the present formulation. Numerical results are presented to illustrate the effect of the porosity distribution on the (SCFs) for various FGPBs. Further, the law of changing the mechanical properties of FG beams without porosity and the SCFare numerically validated by comparison with some available results.

• Structural Engineering and Mechanics
• /
• 제89권1호
• /
• pp.1-11
• /
• 2024

This article introduces a novel analytical model for examining the impact of porosity on shear correction factors (SCFs) in functionally graded porous beams (FGPB). The study employs uneven and logarithmic-uneven modified porosity-dependent power-law functions, which are distributed throughout the thickness of the FGP beams. Additionally, a modified exponential-power law function is used to estimate the effective mechanical properties of functionally graded porous beams. The correction factor plays a crucial role in this analysis as it appears as a coefficient in the expression for the transverse shear stress resultant. It compensatesfor the assumption that the shear strain is uniform across the depth of the cross-section. By applying the energy equivalence principle, a general expression for static SCFs in FGPBs is derived. The resulting expression aligns with the findings obtained from Reissner's analysis, particularly when transitioning from the two-dimensional case (plate) to the one-dimensional case (beam). The article presents a convenient algebraic form of the solution and provides new case studies to demonstrate the practicality of the proposed formulation. Numerical results are also presented to illustrate the influence of porosity distribution on SCFs for different types of FGPBs. Furthermore, the article validates the numerical consistency of the mechanical property changesin FG beams without porosity and the SCF by comparing them with available results.

• 한국콘텐츠학회논문지
• /
• 제7권8호
• /
• pp.182-190
• /
• 2007

가상세계란 전자적 커뮤니케이션에 의해 네트워크화된 3차원 컴퓨터 그래픽 기반의 인터랙티브 환경을 말한다. 오늘날 구현된 가상세계는 기존의 매체에서는 볼 수 없었던 장시간의 몰입을 가능하게 했고, 현실의 노동에 필적할 만큼 힘들고 지루한 장시간의 플레이는 일과 놀이의 경계를 무화시키며 재미노동의 개념을 탄생시켰다. 이러한 재미노동을 '노동을 자연에 가함으로써 자연이 부여한 물리적 한계를 극복하고 자연을 자신에게 더 고유한 존재로 만드는' 인간의 본질로서의 노동으로 긍정한다면, 정보사회에서의 구조적 실업 문제를 해결할 수 있는 획기적인 거대 서비스 분야 중 하나라고 조심스럽게 가정할 수 있다. 또한 재미노동은 돈과 시간과 관심을 지불한 만큼 의미 있는 경험을 하기 원하는 사용자들의 지각 능력과 행위주체성에 부합하는 새로운 형태의 노동일 수 있다. 이러한 현상은 다양한 가상세계를 편력하는 사이버 산책자로서 정의되었던 기존의 사용자 정체성 개념에 반론을 제기하면서, 가상세계의 사용자들은 오히려 하나의 가상세계에 오래 머물며 지속적이고 발전적으로 재미노동을 행하는 존재, 즉 주민의 정체성을 형성하고 있음을 나타낸다. 이렇게 가상세계의 사용자들이 주민성을 형성함에 따라 단체 행동권과 시민참여의 새로운 양식이 확산되어 가고 있으며, 이러한 현상이 사회적으로 미치는 영향을 관찰하는 일이 매우 중요해질 것이다.